One name that surfaced last week as a potential bidder was eBay. But a source close to the company tells us that eBay is not involved in the talks.

So will anyone top Google's $4-$5 billion offer?

Unlikely.

There are only a handful of companies that can afford to buy Groupon and have some strategic reason for doing so.

These include:

Google

eBay

Amazon

Microsoft

Yahoo

Of these, eBay is apparently not involved, Yahoo can't really afford to pay $5 billion, and Microsoft has very little strategic reason to jump into this business. That leaves Amazon and Google.

Amazon buying Groupon would make sense--probably more strategic sense than Google buying Groupon. But we doubt that Amazon would shell out the $5 billion necessary to do it. Amazon's market cap is $75 billion to Google's $190 billion, so the relative cost to the company would be much higher. Amazon is also not as desperately in need of a new growth engine as Google is. So we suspect that if it came down to a bidding war, Google would win.

So now the question seems to be, when Groupon finishes shopping Google's offer, will it decide to pursue an IPO--or take Google's money?

Unless Andrew Mason has an ambition to build the next eBay or Amazon, the answer should be obvious: The company should take the money. $5 billion is not a bad payout for two years work. And there's enough that could go wrong in this business that it's likely worth letting Google and not Groupon take that risk.